The analytical sample preparation process typically involves extraction and clean-up steps: the purpose of the extraction is to transfer components of a sample to a liquid as much as possible to obtain the so-called extract; and the clean-up is to separate the to-be-analyzed components from other components in the extract. The most basic clean-up step is to remove the remaining samples in the extract, which is usually done in a centrifugal manner. The most important step in the extraction process is to thoroughly mix the solids and the liquid to transfer components from the solids to the liquid. The mixing can be achieved in many ways, such as ultrasonic extraction, microwave extraction, and mechanical oscillatory extraction, wherein the mechanical oscillation is the most widely used. The centrifugation method uses high-speed rotation and the centrifugal forces to achieve separation, which is also a purely mechanical method. In most cases, the oscillation and centrifugation involve very different operations, which require different devices, and would not only increase cost, but also require very inconvenient sample transfer. If the two functions can be jointly implemented in a same mechanical device, the analysis sample preparations may be greatly simplified, and their efficiency substantially increased.
At present, there has been report about the use of stepper motor to accomplish oscillation and centrifugal functions. The implementation method includes using a stepper motor as a driving source to produce reciprocating actions at a certain frequency and amplitudes to achieve oscillation, and one-way rotations to achieve centrifugation. This method can only achieve planar oscillations, with their frequencies and angles significantly limited by the performance of the stepper motors, resulting in insufficient vibrations. In addition, the stepper motors have small load capacities, low one-way rotation speed. As a result, the sample processing and the centrifugal speeds cannot fully satisfy the requirements for preparing analytical samples.